1. Field of the Invention
The present invention relates to an improved semiconductor packaging structure and, more particularly, to a packaged semiconductor device which has superior heat transfer characteristic.
2. Prior Art
Various structures have been developed and proposed for reducing heat resistance of semiconductor devices, with a most effective being a structure in which heat generated at the chip is diffused to the exterior of the package only through metals, i.e., without any resin or other insulating material which has small thermal conductivity. Such a semiconductor package structure is disclosed, for example, in Japanese Patent Unexamined Publication Nos. 55-72065, 58-100447, 59-28364, 61-53752 and 62-123748.
In the structures shown in Japanese Patent Unexamined Publication Nos. 55-72065, 58-100447 and 59-28364, the semiconductor element directly contacts heat transfer fins. This type of structure is rather difficult to fabricate in ordinary IC packaging process, though it exhibits superior heat transfer effect. In addition, this type of structure tends to allow water to enter the package along the interface between the metallic part and plastic part of the package, causing a risk for the electrode of the chip to be corroded.
The structures disclosed in Japanese Patent Unexamined Publication Nos. 61-53752 and 62-123748 are easy to manufacture by ordinary IC fabrication process and are free from problems of corrosion of the semiconductor elements. These structures, however, cannot provide sufficient heat transfer effect particularly when, adopted to current large-sized and densely arranged chips which produce large amount of heat.
Structures also have been proposed in which heat is diffused through a seal such as of a plastic or a ceramic. Such structures, however, are inferior in heat transfer characteristic.